In the 90s you could get a light duty 2500 (7200 GVWR), which was basically a ½ ton truck with a ¾ ton rear axle. I have one of those trucks. That rear axle is the 9.5” 14 Bolt Semi Float, which can be had in the regular 6 lug ½ ton pattern. That axle would be a good upgrade to a truck if you wanted to keep the 6 lug pattern. Upgrading the front IFS to the real ¾ ton version though is not practical, so as others have already stated you would be better off starting with a real ¾ ton truck if you want real ¾ ton suspension all around.